This invention relates to a dust control mat article wherein the mat includes one or more layers of rubber. In one embodiment the mat includes at least two layers of rubber, one comprising foam rubber, the other comprising solid rubber. The solid rubber layer is present over the foam rubber layer. Also, at least one integrated rubber protrusion is present to provide cushioning characteristics. The solid rubber layer can act as a cap or barrier for the foam rubber layer, preferably over the integrated protrusion or protrusions. Such a mat is resilient, will not easily degrade in its modulus strength after appreciable use and/or washing within industrial cleaning processes, and will not exhibit appreciable cracking or breaking, particularly within the integrated protrusion(s), after standard use for pedestrian traffic. Methods of producing such inventive cushioned floor mats or articles are also provided. Also, methods of producing mats with flashless protrusions and/or cleats is also provided.
All U.S. patents cited herein are hereby fully incorporated by reference.
As described in Ser. No. 09/374,707, now U.S. Pat. No. 6,340,514, floor mats have long been utilized to facilitate the cleaning of the bottoms of people""s shoes, particularly in areas of high pedestrian traffic such as doorways. Moisture, dirt, and debris from out of doors easily adhere to such footwear, particularly in inclement weather and particularly in areas of grass or mud or the like. Such unwanted and potentially floor staining or dirtying articles need to be removed from a person""s footwear prior to entry indoors. As will be appreciated, such mats by their nature must undergo frequent repeated washings and dryings so as to remove the dirt and debris deposited thereon during use. These mats are generally rented from service entities which retrieve the soiled mats from the user and provide clean replacement mats on a frequent basis. The soiled mats are thereafter cleaned and dried in an industrial laundering process (such as within rotary washing and drying machines, for example) or by hand and then sent to another user in replacement of newly soiled mats.
Uncarpeted anti-fatigue dust control mats have been made in the past comprised of dense rubber, scrap rubber, sponge-like material, including PVC, vinyl polymers, and polyurethanes, as well as recycled tire rubber. The mats are generally not able to be washed in industrial cleaning applications (such as rotary washing machines) since they are either too heavy or dense (and thus either damage the machine or themselves) or either deteriorate too easily (since sponge-like materials are easy to tear apart, particularly in rotary cleaning applications). Such washability is a key to providing a suitable floor mat article within the standard rental laundry market. As such, it has been very difficult to produce uncarpeted cushioned floor mats which exhibit sufficient strength to withstand vigorous cleaning and laundering associated with industrial rental laundry services. Foam rubber has only recently been utilized within dust control mats as a manner of reducing the overall mass of the mat article to facilitate movement and cleaning (such as in U.S. Pat. No. 5,305,565 to Nagahama et al.). Also, cushioned mats have been produced, generally including portions of the mat which contain discrete areas of integrated rubber increasing the surface area of the mat in three axes, which thereby provide cushioned areas on which a pedestrian may step. However, other than as described in Ser. No. 09/374,707, now U.S. Pat. No. 6,340,514 there have not been any mats comprising integrated rubber protrusions which not only permit repeated industrial washings without exhibiting appreciable degradation of the mat structure but also provide excellent cushioning effects to pedestrian users for more comfortable floor and ground covering as well as provide a surface to clean such pedestrians"" footwear.
Further, certain cushioned and non-cushioned (solid) rubber floor mats have experienced problems with flashing, flaring, or hooks at the top edges of the protrusions, cleats, or the like (FIGS. 48-50) depending on the mat construction and manufacturing process. Flashing tends to be aesthetically displeasing. Also, flashing may deleteriously effect the functioning of the mat. Slight flashing tends to rub or come off of the mat following use of or washing of the mat. Although numerous attempts have been made to reduce or eliminate flashing on rubber floor mats, most such attempts have been unsuccessful at totally eliminating flashing or have proven too costly and/or complicated to implement. One successful approach to reducing flashing on cleats of a cleated mat is described in above-mentioned U.S. patent application Ser. No. 09/405,883, filed Sep. 24, 1999, now U.S. Pat. No. 6,303,068.
Hence, there is a need for an improved flashless mat or article and method of producing such a mat.
It is thus an object of this invention to provide a flashless or reduced flash floor mat and method. Further, it is an object to provide a flashless, durable, dust control mat which permits cleaning of a pedestrian""s footwear. Furthermore, it is an object of the invention to provide a flashless, durable, cushioned dust control mat in which the cushioning aspects are provided by at least one integrated rubber protrusion produced during the necessary vulcanization process. Still other objects of the invention is to provide a flashless cushioned all-rubber floor mat which retains its cushioning characteristics and shape upon use and can be laundered repeatedly within industrial rotary washing machines without damaging such machines or themselves.
Accordingly, one embodiment of this invention encompasses a rubber floor mat structure comprising at least two separate layers of rubber wherein said at least two layers comprise
a first layer comprised of foam rubber; and
a second layer comprised of solid rubber;
wherein at least one protrusion integrated within said rubber mat structure is present having a core portion and an outside surface portion, wherein the core portion of said at least one protrusion is comprised of said first layer of foam rubber, wherein the outside surface portion of said at least one protrusion is comprised of said second layer of solid rubber, and wherein said at least one protrusion is substantially flashless.
The first rubber layer may be comprised of any standard rubber composition, including, but not limited to, acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR), carboxylated NBRB, carboxylated SBR, chlorinated rubber, silicon-containing rubber, and the like, all of which must include a blowing agent to form the necessary closed-cell structure of the resultant foam rubber, such as in U.S. Pat. No. 5,305,565 to Nagahama et al. For cost purposes, the preferred rubbers are NBR, SBR, and blends thereof.
As noted above, the foam rubber component is of utmost necessity in a cushioned floor mat. Dust control mats have exhibited general problems arising from frequent washings and harsh environments of use. First, the energy required to wash and dry a typical floor mat is significant due to the overall mass of the mats. The overall mass is most significantly attributed to the mass of the rubber within the mat. As will be appreciated, a reduction in the overall mass of the floor mat will result in a reduced energy requirement in washing and drying the mat. Moreover, a relative reduction in the mass of the rubber will provide the most substantial benefit. Thus, the utilization of a lighter weight rubber composition, such as foam rubber, in at least a portion of the dust control mat of the present invention includes a rubber backing sheet which may possess a specific gravity which is approximately 25 to, 35 percent less then the rubber sheets of typical prior floor mats. Accordingly, in at least one embodiment, a foam rubber is used as the bottom layer of the mat and the core layer of the integrated rubber protrusion(s) of this invention. Such a foam rubber layer is present as a thicker layer than the solid rubber cap (generally). The target thickness for such a first layer is from about 5 to about 500 mils, preferably from about 25 to about 400 mils, more preferably from about 40 to about 350 mils, and most preferably from about 75 to about 250 mils.
The resultant lighter weight of the mat structure thus translates into a reduced possibility of the mat harming either the washing or drying machine in which the mat is cleaned, or the mat being harmed itself during such rigorous procedures. Although the inventive floor mat must withstand the rigors of industrial machine washing, hand washing and any other manner of cleaning may also be utilized. Foam rubber also permits the retention or return to the original shape of the mat after continuous pedestrian use. Overall, the inventive floor mat provides an article which will retain its aesthetically pleasing characteristics over a long period of time and which thereby translates into reduced costs for the consumer.
In accordance with at least one embodiment, at least a second rubber layer comprises a solid rubber composition. Such a solid rubber may be comprised of any standard type of rubber, such as acrylonitrile-butadiene (NBR) or styrene-butadiene (SBR), or carboxylated derivatives of such butadienes, EPDM, and the like (i.e., those noted above but without the addition of a blowing agent), all merely as examples. Preferably, the second layer is comprised of NBR. The target thickness for such a second layer is from about 2 to about 50 mils, preferably from about 4 to about 40 mils, more preferably from about 5 to about 35 mils, and most preferably from about 10 to about 25 mils. This layer is preferably placed on at least the top of the foam rubber first layer as to cover the entire first layer prior to vulcanization. However, this second layer may also merely cover a portion of the first layer, if desired. Once the second layer is placed directly on top of the first layer, a die mold, plate, belt, or the like, is then placed on top of the second layer which comprises openings through which molten rubber may flow during vulcanization and pressing of the structure. The high pressures (about 15 to about 50 psi, preferably 20 to 40 psi) and temperatures (about 250 to about 400xc2x0 F., preferably from about 320 to about 385xc2x0 F.) associated with vulcanization thus melt and force a certain amount of the two layers through the die mold or plate openings. The denser solid rubber does not permit the less dense blown foam rubber to protrude through the solid rubber layer during this procedure. As such, the resultant protrusions preferably possess foam rubber cores and solid rubber caps. Such protrusions add to the overall surface of the top (or bottom) of the mat structure, thus the solid rubber layer is appreciably thinner after vulcanization and molding than after the initial placement step. However, the solid rubber layer still remains intact and possesses sufficient strength to protect the foam rubber from contact with pedestrians"" footwear, atmospheric conditions, and sunlight. The resultant mat thus is intended to be used with the capped protrusions facing toward the pedestrian. However, a die mold, plate, belt, or the like, may also be placed beneath the unvulcanized structure such that protrusions or cleats may be formed on both sides (with or without a solid rubber layer capping such foam rubber protrusions), as desired. The inventive mat includes one or more layers, and preferably possess at least a two-layer structure with accompanying protrusions therein.
Furthermore, a problem exists within this field concerning the deterioration of the carbon-carbon double bonds in the matrix of the rubber backing sheet due to the exposure of the sheets to an oxidizing environment during use and cleaning. Specifically, the exposure of the mats to oxidizing agents during the washing and drying process tends to cleave the carbon-carbon double bonds of the rubber sheet thereby substantially embrittling the rubber which leads to cracking under the stress of use. In addition to the laundering process, the exposure of the mats to oxygen and ozone, either atmospheric or generated, during storage and use leads to cracking over time. The mat of the present invention may thus include an ozone-resistance additive, such as ethylene-propylene-diene monomer rubber (EPDM), as taught within U.S. Pat. No. 5,902,662, to Kerr, which provides enhanced protection to the rubber backing sheet against oxygen in order to substantially prolong the useful life of the mat. Such an additive also appears to provide a reduction in staining ability of such rubber backed mats upon contact with various surfaces, such as concrete, wood, and a handler""s skin, just to, name a few, as discussed in U.S. patent application Ser. No. 09/113,842, now U.S. Pat. No. 6,159,576 to Rockwell, Jr.
The term xe2x80x9cintegrated rubber protrusionxe2x80x9d is intended to encompass any type of protrusion from the rubber mat (top and/or bottom) which is formed from the same rubber compositions of the foam rubber layer, solid rubber layer, or two or more separate layers of rubber and is not attached in any manner to the resultant backing sheet after vulcanization. Thus, such a protrusion would be produced through the melting of the rubber composition during vulcanization and allowing molten rubber to flow into or through a die mold, plate, or belt in a position in which it remains until it cures and sets. The shape of such a protrusion is virtually limitless, and may be of any size. As noted above, the majority of the mat structure (the first layer) is preferably a rubber including a blowing agent (to produce a foam rubber) and at least a second layer of solid rubber covers this foam rubber portion. In such a manner, the protrusions on at least one side of the mat are formed with a core of foam rubber and a cap of solid rubber upon vulcanization through a die-mold. The separate protrusions thus provide discrete areas of relaxed stress within the inventive mat (particularly with the core of softer foam rubber) which provides a cushioning effect to a pedestrian, greater than for an overall flat foam rubber structure.
With regard to the protrusion forming die mold, plate, belt, pad, or the like, it may be constructed of any material which can withstand vulcanization temperatures (i.e., between about 250xc2x0 F. and about 400xc2x0 F.) and pressures (i.e., between about 15 psi and 50 psi, generally). Thus, any metal may be utilized, such as steel, aluminum, titanium, and the like, certain plastics, such as Teflon(copyright), for example, silicon molds, and the like.
Also, as described in U.S. patent application Ser. No. 09/405,883, filed Sep. 24, 1999, now U.S. Pat. No. 6,303,068 hereby incorporated by reference, different belting materials may be used such as fiberglass coated with Teflon(copyright). Preferably, the die mold or plate is made of steel or aluminum, is generally square or rectangular in shape (although any shape may be utilized), may have rounded comers, and comprises holes throughout to ultimately form the desired protrusions. Such holes may be any shape, such as circular, polygonal, oval, elliptical, lobed, or the like, and preferably, such holes are substantially circular or rounded in shape (at the die surface) and cylindrical as well (i.e., circular on both surfaces with the same shape throughout the die from one surface to the other). Furthermore, such a die may also be utilized in an in-line process wherein there is no need to hand place the backing sheet over the die itself. Also, a die, plate, belt, pad, or the like may be placed below the rubber to be vulcanized to form protrusions or cleats on the top and/or bottom of the mat. The preferred procedure is outlined more particularly below.
The inventive mat provides a long-lasting, industrially washable, cushioned rubber floor mat which provides comfort to users as well as significantly increased duration of utility and continuity of aesthetic and modulus strength characteristics. All of this translates into reduced cost for the consumer as costs to produce are lower, the need to replace such mats is greatly reduced over other anti-fatigue, cushioned mat products, and possible medical and insurance costs may also be reduced with the utilization of such specific cushioned mats which also work to remove dirt and moisture from pedestrians"" footwear.
In accordance with one embodiment of the invention, any flashing problems on the surface of the protrusions and/or cleats of the mat are improved, reduced, or eliminated.
In accordance with one example of reducing or eliminating flashing on the mat, a new manufacturing process was developed. As before, holes cut into the plate can be round, square, other polygons, or any other variant. The surface pattern is molded into the mat during vulcanization by using a plate in which the pattern is cut. In the mat make-up process, the plate is placed on top of the uncured rubber and a special release sheet, material or liner is placed over the plate. The special material allows air to escape during formation of the protrusion, but limits the flow of rubber or other mat material so that it does not flow past the point of where the intended protrusion was to form. In other words, the resulting protrusions have the dimensions very close to that of which was intended and have very little excess material present. When the rubber is vulcanized, the rubber flows up into the holes in the plate to create the pattern. After vulcanization the liner and plate are removed.
In accordance with an example of improving the non-slip or anti-creep characteristics of the mat, the back of the mat may either have a rough texture surface, a smooth surface, or a gripper pattern depending on the environment in which the mat is to be used.
One purpose of the invention is to create an improved version of the washable anti-fatigue mat of foam rubber with/without a dense rubber cap that has improved non-slip, anti-creep, anti-skid, anti-microbial, and/or other characteristics. The added or improved characteristics of the invention will give it an advantage over other products because it can be used in wet or slick environments where mat slippage is a concern.
One aspect of the present invention relates to specific methods of producing cleated rubber-backed floor mats (such as dust control or rubber mats) through the utilization of the combination of a perforated coated woven fabric article or belt and a special release sheet material or liner between the fabric article and the metal platen of an in-line dust control mat manufacturing machine. Such a procedure permits an efficient manner of producing substantially flashless cleated anti-creep (anti-skid) dust control mats. In one embodiment, the fabric article is in the form of a conveyor belt and is preferably constructed from Teflon(copyright)-coated or PTFE-coated woven fiberglass which will not adhere to the tacky rubber component of the target mat and can withstand the extremely high vulcanization temperatures and pressures required during the production of a dust control mat. The platen liner, which is preferably comprised of or coated with Teflon(copyright) or silicon, is utilized as a separator between the metal platen of the manufacturing machine, as well as a cushion for the molten rubber as it is pressed through the belt perforations during vulcanization. Such a special liner material substantially eliminates any flashing problems by blocking passage of the molten rubber as it passes through the article perforations. The produced mat as well as the woven fabric article and platen liner combination are also encompassed within this invention.
Floor mats have long been utilized to facilitate the cleaning of the bottoms of people""s shoes, particularly in areas of high pedestrian traffic such as doorways. Moisture, dirt, and debris from out of doors easily adhere to such footwear, particularly in inclement weather and particularly in areas of grass or mud or the like. Such unwanted and potentially floor staining or dirtying articles need to be removed from a person""s footwear prior to entry indoors. As will be appreciated, such outdoor mats by their nature must undergo frequent repeated washings and dryings so as to remove the dirt and debris deposited thereon during use. These mats are generally rented from service entities which retrieve the soiled mats from the user and provide clean replacement mats on a frequent basis. The soiled mats are thereafter cleaned and dried in an industrial laundering process (such as within rotary washing and drying machines, for example) and then sent to another user in replacement of newly soiled mats. Furthermore, it is generally necessary from a health standpoint to produce floor coverings on which persons may stand for appreciable amounts of time which will provide comfort to such persons to substantially lower the potential for fatigue of such persons by reducing the stress on feet and leg joints through cushioning.
Typical carpeted dust control mats comprise solid and/or foam rubber backing sheets which must be cleated in some manner to prevent slippage of the mat from its designated area. Such cleats are formed during a vulcanization step and have required a time-consuming procedure of placing the green (unvulcanized) rubber sheet on a molded, perforated silicon pad or perforated metal plate which is itself placed by hand on the conveyor belt of a dust control manufacturing apparatus. The finished mat is then removed after vulcanization from the non-stick silicon pad. The resultant mat product possesses cleats formed through the melting and forcing of part of the rubber backing through the pad perforations during vulcanization. Such cleats provide anti-slip or anti-creep characteristics to the finished mat when placed upon a surface to be protected. Various types, shapes, and arrangements of cleats have been utilized in the past with dust control mats. Examples include U.S. Pat. No. 4,741,065 to Parkins, U.S. Pat. No. 5,170,526 to Murray, and U.S. Pat. No. 5,227,214 to Kerr et al.
As noted above, previous methods of providing such cleat features to rubber-backed mats are generally produced through the utilization of a perforated silicon pad which is placed by hand on a conveyor belt in an in-line vulcanization apparatus. A rubber article is then placed on top of the silicon pad, and optionally a fabric pile (such as a carpet) is then placed, again by hand, on top the rubber article. The conveyer belt then transports the entire composite to a vulcanization chamber wherein it is pressed at a pressure of from about 25 to about 40 psi at a temperature of from about 300 to about 400xc2x0 F. for anywhere between about 30 seconds and 20 minutes. After vulcanization, the conveyor belt transports the finished composite (floor mat plus silicon pad) out of the chamber. The floor mat is then removed from the pad and allowed to cool and the pad is moved, by hand, back to a location on the conveyor belt, prior to the chamber, in order for another rubber article to be placed thereon. Such a procedure is labor-intensive and inefficient.
In view of the foregoing, it is one object of the present invention to provide an in-line method for the production of cleats and/or protrusions in a rubber or rubber-backed floor mat. Furthermore, it is an object of this invention to provide a novel conveyor belt system for an in-line floor mat manufacturing apparatus. Additionally, an object of this invention is to provide a cleated anti-creep floor mat which is more easily and efficiently produced than standard cleated floor mats. Still another object of this invention is to provide an anti-creep floor mat which exhibits not only cleats to provide anti-slip characteristics, but also intermittent patterned areas within the rubber on the underside of the rubber floor mat component which mirrors the woven structure of the perforated fabric article or belt.
Accordingly, this invention encompasses a method of producing a substantially flashless cleated anti-creep floor mat comprising a rubber mat component with a mat producing apparatus comprising the steps of:
(a) providing a perforated woven fabric article, which is coated or comprised of a material which will not adhere to said rubber mat component after a vulcanization step, wherein said perforated woven fabric article is optionally separated from the metal platen of said apparatus by a platen liner;
(b) placing said rubber mat component on top of said perforated woven fabric article of step xe2x80x9caxe2x80x9d and optionally placing thereon a fabric pile, a die mold, or a die mold followed by a release sheet;
(c) transporting the rubber mat component/perforated woven fabric article composite to a vulcanization chamber; and
(d) vulcanizing said rubber mat component as it remains on top of the perforated woven fabric article, thereby forming cleats through the perforations of said perforated woven fabric article;
wherein said woven fabric article, platen liner and release sheet are comprised of or coated with materials which can withstand the temperatures and pressures associated with vulcanization.
Also, this invention concerns a floor mat manufacturing apparatus having a metal platen wherein said apparatus further comprises a perforated conveyor belt positioned on top of a cushioned platen liner which is positioned on top of said metal platen.
Additionally, this invention encompasses a floor mat article comprising at least a rubber sheet component wherein said rubber comprises a plurality of substantially flashless cleats formed integrally on the surface and at least a portion of the surface of said rubber sheet also comprises a weave pattern of molded rubber.
The term xe2x80x9cperforatedxe2x80x9d or xe2x80x9cperforationsxe2x80x9d is intended to encompass any configuration of holes or openings within the woven fabric article structure through or into which molten rubber may be forced during vulcanization. Thus, any shape hole, any orientation of holes, and any depth of such holes is encompassed within such a term. Preferably, the holes (perforations) are circular or rounded in shape ultimately to produce cylindrically or rounded shaped cleats in the target mat article. Also, the diameter of such perforations are preferably from about {fraction (1/64)} inch to about xc2xd inch; more preferably from about {fraction (1/32)} inch to about xc2xc inch; and most preferably from about {fraction (3/32)} to about {fraction (1/16)} inch. The preferred thickness of the fabric article and resultant cleats is from about 10-100 mils, preferably about 20-90 mils, more preferably about 30-60 mils, and most preferably about 30-40 mils.
Preferably, the perforated woven fabric article of the instant invention is present in the form of a conveyor belt which thereby permits an in-line mat production procedure. In such a form, a platen liner (or release sheet) should be utilized under the conveyor belt in order to reduce off-quality cleat production, as discussed below. However, if desired, the woven fabric article may also be a separate article which is cut from a web of fabric which can be placed by hand on top of a cushioned platen liner and/or on a conveyor belt within a mat manufacturing apparatus. After vulcanization, the finished mat can easily be removed from the fabric article and the fabric article can then be transported to a pre-vulcanization location for placement of another rubber mat component thereon. The preferred fabric belt or article of the instant invention should be constructed of material which not only can withstand continuous and/or repeated movement around a rotating drum and through a standard in-line floor mat manufacturing apparatus, but such materials (including the cut-out forms of such woven fabric articles) should also be able to withstand the high temperatures and pressures associated with rubber vulcanization. The core material of such a belt or cut-out is thus preferably fiberglass although other materials, such as polyaramids, silicon, and the like, may also be utilized. The belt or cut-out should also be coated with a covering which can also withstand vulcanization temperatures and pressures and not appreciably adhere to molten rubber. Silicon or silicon rubber may be utilized for this purpose as well; however, the preferred coating is polyfluoroethylene, also known as Teflon(copyright), available from DuPont.
The preferred conveyor belt (or cut-out fabric) is first produced by taking a woven (or non-woven) fiberglass fabric and coating it with a certain number of polytetrafluoroethylene (PTFE) or Teflon(copyright) layers. Perforations are then cut into the coated fabric to conform with the desired shape and orientation of ultimately formed cleats on the target floor mat or article. Then, the cut fabric is coated with a few more layers of Teflon(copyright) in order to insure the potentially frayed fibers of the cut fiberglass will not interfere with the eventual removal of the target floor mat article from the belt surface. If such frayed fiber ends were not coated themselves, they could adhere to the mat and produce aesthetically displeasing results. The coated fabric, and thus the belt itself, may have a thickness of from about {fraction (1/64)} inch to about xc2xd inch, depending on the desired size of the ultimately formed cleats or protrusions. The thickness of the fabric (belt) dictates the length of the projected cleats from the rubber surface of the mat article since, upon melting during vulcanization, the rubber will become forced through the perforations of the belt a distance roughly the same as the belt thickness. Preferably, the cleat lengths are from about {fraction (1/64)} to xc2xd inch, more preferably from about {fraction (1/32)} inch to about xc2xc inch; most preferably about {fraction (2/32)} inch to about {fraction (3/32)} inch.
The woven or non-woven structure of such a fabric article provides an extra anti-slip weave pattern feature to the finished floor mat product. Since woven or non-woven fabrics exhibit differing textures at their surfaces due to the interlacing and crossovers of the individual yams within the structure, the mirror image of such a woven or non-woven structure will be transferred to the target rubber mat component during vulcanization as long as the fabric article remains in place under the rubber component during such a step. In the past, the production of cleats has been performed, as noted above, with silicon pads, and the like, which produced discrete cleats within the rubber mat component but generally did not include any anti-slip features between such produced cleat formations. Through the utilization of such a woven or textured structure, the resultant fabric pattern or texture can thus be transferred to the rubber surface which provides a roughened surface between produced cleats or protrusions for improved anti-slip characteristics or aesthetics within the inventive floor mat.
Prior to incorporating the aforementioned preferred conveyor belt to a floor mat manufacturing apparatus (which generally comprises a metal platen over which the conveyor belt would be placed directly), a platen liner is placed over the metal platen. A platen liner may be placed beneath a hand-placed fabric article on a conveyor belt, or placed within a shelf-type vulcanization chamber.
In general, it has been discovered that the platen liner should be present to avoid the creation of xe2x80x9cflaredxe2x80x9d cleats or flashing in the final mat product. Such a problem is caused by both the lack of adhesion between the molten rubber and the Teflon(copyright)-coated fabric surface as well as the force of the metal platen liner on the molten rubber forced through the fabric perforations. Without a cushioning platen liner or sealing liner, when the vulcanization chamber presses down on the mat article, the rubber, upon melting, is forced through the perforations toward the metal platen. The force of the stationary metal platen then forces the rubber back toward the belt and rubber article; however, the molten rubber will seek the path of least resistance rather than returning through the perforation it came originally. Without the adhesion between the fabric and the rubber, the rubber will easily move between the fabric and the platen. In such an instance, upon exiting the vulcanization chamber, the mat article is not easily removed from the belt (since the rubber forms flashing, flares or xe2x80x9chooksxe2x80x9d on the underside of the belt). The resultant mat article thus exhibits aesthetically displeasing cleat formations which themselves possess suspect effectiveness at preventing slippage or creeping of the mat when placed on a protected surface. Hence, it was discovered that in order to provide such an efficient procedure of in-line cleat forming for floor mat articles, a cushioned platen liner was used to separate the fabric article (belt) from the metal platen and to provide cushioning of the rubber to prevent re-forcing back toward the belt itself during vulcanization. However, such a platen liner may not be required when a cut-out article is utilized to produce the desired cleats, most notably when the conveyor belt itself (which may be coated rubber, or other fabric, for example) within the mat manufacturing apparatus provides the necessary cushioning effect; but, other times there will be a need to utilize such a cushioned and/or special liner to reduce the production of off-quality cleats.
When present, the platen liner preferably covers the entire area of the metal platen over which mat articles will be placed. Preferably, the platen liner will possess a modulus of from about 40 to 70 on the Shore A Hardness Scale in order to provide the necessary cushioning effects for proper cleat formation. Preferably, the modulus is about 50 on the same scale. Furthermore, the platen liner must be able to withstand the high temperatures and pressures associated with rubber vulcanization. Thus, the liner must be constructed from material which possesses both characteristics. The preferred material is a rubber coated with silicon (available from Taconic, for example) which exhibits a Shore A Hardness of about 50. However, the liner may also be constructed from other heat-resistant materials which have been incorporated within flexible fabrics, rubber, and the like, and/or alternatively coated with a heat-resistant material, such as Teflon(copyright), silicon, and the like. The thickness of such a liner is not of great importance, although, the thicker the better (for cushioning purposes). The utilization of too thick a liner will not seriously impact the effectiveness of the perforated conveyor belt in producing the desired cleats; however, as silicon liners are rather expensive, the thickness should be dictated primarily by cost versus available cushioning characteristics. As such, the liner may have a thickness of from about {fraction (1/64)} inch to about xc2xd inch. A thickness of about {fraction (1/64)} to about xe2x85x9 inch is preferred; and {fraction (1/64)} inch to about {fraction (3/32)} inch more preferred, and about 30-40 mils is most preferred.